A fiber supercontinuum light source can generate wideband light featuring high brightness and high coherence, and is equivalent to a wideband laser. The fiber supercontinuum light source has a bright application prospect in fields such as biomedicine, laser spectroscopy, environmental monitoring, and remote sensing.
Ultra-wideband spectral output is a core goal of the study on supercontinuum. However, to generate a wideband supercontinuum, a wavelength of a pump laser should be located in a fiber anomalous dispersion region and be closest to a fiber zero dispersion wavelength (Zero Dispersion Wavelength, ZDW), so that an ultra-short pulse evolved from the pump is easily extended to a normal dispersion region. Currently, a mainstream technology for generating a supercontinuum is pumping a silica fiber or a non-silica fiber by using a 1 μm or 1.5 μm/2 μm high-power fiber laser.
Fibers matching 1 μm ytterbium (Yb)-doped fiber laser are silica photonic crystal fibers (Photonic Crystal Fibers, PCF). By pumping the silica PCF with a 1 μm ytterbium (Yb)-doped fiber laser, a supercontinuum that covers a short-wavelength visible band can be generated, but a powerful infrared absorption function of the silica material restricts the supercontinuum from covering a long wavelength band. Consequently, the spectral energy mainly focuses on visible and near-infrared bands and is difficult to cover a band of over 2.5 μm.
Fibers matching 1.5 μm or 2 μm fiber laser are non-silica glass fibers (fibers made from fluoride, chalcogenide or other materials). In high-power pumping, the non-silica glass fibers can generate a supercontinuum that covers a long-wavelength 5 μm mid-infrared band. However, because the fiber zero dispersion wavelength and the pump wavelength are located at a long-wavelength band of over 1.5 μm, the supercontinuum generated in the non-silica glass fibers is difficult to cover a short wavelength band of less than 0.8 μm, and the spectral energy mainly focuses on an infrared band of over 1 μm.
Therefore, by using a technology in which a single-band laser pumps a fiber made from a single material, the supercontinuum is difficult to extend to a visible band and a mid-infrared band simultaneously, thus hindering the implementation of an ultra-wideband supercontinuum covering visible, near-infrared, mid-infrared bands.